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N HOZ/02- + Fe2+ + W 4 Fe3+ + H2O2 Where, H202 = Hydrogen Peroxide, Fez+ = Ferrous Ion, Fe3+ = Ferric Ion, 011e = Hydroxyl Radicals The by-products for this process are carbon dioxide and water. The hydroxyl radical that attacks the carbon-hydrogen and other recalcitrant compounds such as MTBE. The Fenton's chemistry reaction is highly complex, The iron cycles between the Fe(II) and Fe(IU) oxidation states yields the hydroxyl radical and other by products (Suthersan, 2002). Residual H202not used in the oxidation process breaks- down to water and oxygen in a matter of hours. In addition to the reaction described in Equation 2, there are also a large number of competing reactions including the free radical scavengers, most importantly, carbonate and bicarbonate alkalinity, that will greatly affect the overall reaction scheme. In addition, H2O2 can serve as an oxygen source for microbes in the subsurface to enhance biodegradation of contaminants. Although handling hydrogen peroxide and other oxidants requires significant safety training and planning, the oxidant is effective at remediation of a variety of organic contaminants and is relatively inexpensive. The reaction time for hydrogen peroxide in E1 the subsurface is within minutes to at most, hours. Rise in temperatures in the subsurface illustrates the exothermic nature of the oxidation process. Rapid degradation of hydrocarbons, solvents and organic compounds is the goal of in-situ chemical oxidation, not the violent decomposition of hydrogen peroxide which does occur at elevated reaction temperatures. ydrogerrperoxide-reacts--in--an-optimal-manner-in-4owe"11--settings with-lowe alkalinity readings. In some cases, acids are used to lower pH. The end products of oxidation are carbon dioxide and water. Trace chloride from chlorinated compounds will likely combine with sodium or calcium ions to form salts or with hydrogen to form weak acids. Careful evaluation of soil and water chemistry using a bench test (Figure 1) with soil and water samples is recommended prior to the start of any injection process. Due to the rapid reaction time, subsurface spacing of injection ports must be relatively close which is dependent on lithology. Clays and silts which are problematic to remediate in-situ, typically require 3 to 5 foot spacing, whereas injection ports for clean sand and gravels can be placed at 10 to 15 foot spacing, which is the case for this site. For in-situ chemical oxidation, the metal catalyst is usually provided by iron oxides within the soil or fill material, or added separately as a solubilized iron salt, such as iron sulfate. In addition, pH adjustment using an acid such as sulfuric acid (H2SO4), hydrochloric acid (HCl), or others are common since the chemical oxidation is more rapid and efficient under lower pH conditions (pH 2-4 is optimal). Fenton's chemistry has been well documented for over 100 years and has been in use in water treatment plants for over 50 years. The supportive chemical processes which essentially results in 3